I found this tee on sale at Cabela's. I was looking for something comfortable in this hot and very humid weather. The shirt seems like it might work, though I think a long sleeved version would be better for cool weather and for sleepwear. The fabric is a light knit but seems quite durable and more snag/pill resistant than other brands I have tried. I have worn it for a week and it still smells ok. My large weighs about 5.5 ounces. Here is a link to search by the item number:

Medalist® Silvermax™ Silkweight Short-Sleeve Crew
ITEM: 9IS-960842

There are several types of shirts and fabrics listed, but I think mine is the silkweight. The regular weight does not seem much heavier though.